DOC: to_sql and extending pandas

[achapkowski]

• I have checked that the issue still exists on the latest versions of the docs on master here

Location of the documentation

https://pandas.pydata.org/pandas-docs/stable/development/extending.html

Documentation problem

When you create a custom Dtype with Pandas and you need to use the to_sql (write to a sqlite database), it is unclear how you can handle the custom dtypes. If at all from the documentation.

This is the error you get with custom datatypes:

File "pandas_libs\lib.pyx", line 1229, in pandas._libs.lib._try_infer_map
AttributeError: 'MyCustomType' object has no attribute 'base'

So does something on the Dtype or on the ExtensionArray need to define base and what is base?

Suggested fix for documentation

Explain if custom dtypes is supported with to_sql.